Who crafted Thor’s hammer in Norse mythology?

Mjollnir, Old Norse Mjöllnir, in Norse mythology, the hammer of the thunder god, Thor, and the symbol of his power. Forged by dwarfs, the hammer never failed Thor; he used it as a weapon to crash down on the heads of giants and as an instrument to hallow people and things.

answer; (d) i believe that the correct answer is americans finally ran out of ammunition;